The photosynthetic membranes, or thylakoids, found within the chloroplasts of green plants are highly specialized structures which carry out the direct conversion of light to chemical energy in photosynthesis. The research outlined in this proposal is intended to develop our understanding of the structural organization of this membrane in such a way that meaningful correlations can be made between the structure, biochemistry, and biophysics of the thylakoid. Investigations using the freeze-etching technique, which has aided in the development of our current conception of thylakoid structure by the visualization of a wide variety of particulate subunits in the membrane, will be carried out on a number of mutants which are known to be missing certain components of the photosynthetic apparatus. In this way we should be able to correlate specific structures in the membrane with various elements of the photosynthetic process. These studies will be correlated with biochemical and energetic analyses of the membrane. Photosynthetic membranes which have been greened in unusual ways, which have been treated with inhibitors of oxygen evolution, and which have been oriented in strong magnetic fields will also be examined for structural changes. A final point will be a series of attempts to induce the formation of reproducible particle lattices in the membrane. Success in this will make possible the mapping of membrane structure at very high resolution, which is the ultimate aim of this work.